Dengue fever is a vector-borne disease assuming endemic proportions in the Indian subcontinent and Southeast Asia. It was first reported in 1789 by Benjamin Rush who gave the name “break bone fever” to describe the condition due to its association with joint pain.[1] In the late 1900s, there was a rapid increase in the cases of dengue fever leading to major epidemics in many parts of the world. Currently, as per the WHO, half of the world's population is at risk of dengue fever with nearly 50–100 million people being affected annually in over 100 endemic countries.[2] Because of the rapid increase in incidence and widespread prevalence, dengue has become a major public health concern. The WHO launched “The Global Strategy for Dengue Prevention and Control 2012–2020” to address this threat of an impending pandemic and reduce the burden of dengue.[3]

Dengue fever spreads from the bite of an infected female Aedes mosquito, primarily Aedes aegypti species and Aedes albopictus. It is caused by a positive-stranded encapsulated RNA virus belonging to the family Flaviviridae. Dengue virus has four serotypes, namely, DEN-1, DEN-2, DEN-3, and DEN-4 and infection with all four is responsible for dengue fever. Infection with one serotype does not provide immunity from other serotypes but prevents re-infection from the same serotype. Repeated infections increase the risk of severe dengue.[1],[2]

With increase in the number of cases of dengue, there are reports of different neuropsychiatric manifestations associated with this condition from different parts of the world. The exact incidence of neuropsychiatric manifestation is, however, not certain due to lack of adequate studies. The psychiatric symptoms may accompany the acute phase of dengue or can be a late manifestation. There have been numerous case reports of appearance of manic symptoms during febrile phase of dengue fever as well as in convalescence period.[5],[6],[7],[8] Patients generally presented with talkativeness, authoritative and irritable behavior, grandiosity, increased sexual behavior, and reduced need for sleep, and symptoms were controlled rapidly within a week to month in all cases with mood stabilizers and antipsychotics. Only a few cross-sectional hospital-based observational studies have been conducted in acute dengue patients to evaluate for common mental disorders. Anxiety was found to be a prominent finding in all these studies.[9],[10],[11] In the acute phase of the illness, nearly 90% of the patients exhibited thanatophobia (fear of death), 15-23% had panic attacks, and overall 80% had significant anxiety-related symptoms.[9],[11] These symptoms, however, reduced in severity and frequency as the physical condition improved and only a few needed anxiolytics. However, about 50% of these patients developed insect phobia on recovery from dengue fever.[9],[11] Depressive symptoms were observed in 50%–60% patients initially which came down to about 5%–20% once the acute phase was over.[9],[10],[11] All the studies demonstrated a significant female preponderance for depressive and anxiety symptoms.[9],[10],[11] Hashmi et al. 2012 even showed that the depressive and anxiety symptoms were positively correlated to the severity of fever, headache, joint pain, body ache, and retro-orbital pain.[10] Dengue-related psychosis has also been reported in literature. It can present during the acute phase as reported in this case report “Psychosis in Dengue Fever” published in this issue or can be a late manifestation.[12],[13],[14] The symptoms reported are visual/auditory hallucinations, persecutory hallucinations, emotional lability, agitation and disturbed sleep, appetite and self-care. There was rapid resolution of psychosis with low doses of antipsychotics in all these reports. Only two cases of catatonic symptoms in dengue have been reported in published literature so far.[15],[16] Mutism, stupor, posturing, and negativism were the prominent findings in both the cases.

The dengue virus has been known to cause capillary leakage leading to accumulation of fluid in the extravascular space and cerebral edema.[1] This has been hypothesized to be the cause of the neurological manifestations such as encephalopathy, delirium, and paraparesis in severe dengue. Recent evidence of virus isolation from brain tissue, however, indicates dengue neurotropism. Other possible explanations are systemic effect of dengue infection or neuroimmune-mediated response.[17] Increased cytokine levels have also been reported in systemic conditions associated with anxiety and depressive symptoms as well as in dengue fever and can thus be hypothesized to be responsible for psychiatric manifestations in the latter.[18]

Although the exact mechanism of neuropsychiatric manifestations in dengue infection remains unclear, increasing reports of the same makes it imperative to screen patients with dengue fever for psychiatric morbidities.